PR #84594: Fix incorrect SSG classification for dynamic pages with generateStaticParams

• Repository: vercel/next.js
• Author: wyattjoh
• State: closed | merged: False
• Link: https://github.com/vercel/next.js/pull/84594

Description (problem / solution / changelog)

Fixing a bug

• Related issues linked using fixes #84584
• Tests added - regression test in test/production/app-dir/static-rendering-with-connection/
• Errors have helpful links (N/A for this fix)

What?

Fixes a bug where pages with generateStaticParams that use dynamic APIs (cookies(), headers(), connection()) were incorrectly marked as SSG (●) in the build output, when they should be marked as Dynamic (ƒ).

Why?

This was causing users to mistakenly believe their pages were statically generated when they were actually rendered dynamically at request time. This led to confusion about deployment behavior and performance characteristics, as reported in #84584.

The bug occurred because the dynamic detection check ran before individual routes were processed during the build. The check looked at the pattern route (e.g., /blog/[slug]) which was never actually rendered, causing it to incorrectly return false for hasRevalidateZero. When the actual routes were processed later (e.g., /blog/post-1), they correctly detected revalidate: 0, but by then the parent page had already been classified as SSG.

How?

Added a second check in packages/next/src/build/index.ts after processing all prerendered routes. If any routes have revalidate: 0 (indicating they're dynamic), the parent page classification is corrected from SSG to Dynamic.

The fix includes:

• Post-processing logic to correct page classification when routes turn out to be dynamic
• Regression test with snapshot validation of build output
• Test covers both standard mode and cache components mode (PPR)

Fixes #84584

NAR-430

Changed files

• packages/next/src/build/index.ts (modified, +11/-0)
• test/production/app-dir/build-output-tree-view/build-output-tree-view.test.ts (modified, +70/-0)
• test/production/app-dir/build-output-tree-view/fixtures/dynamic-generate-static-params/app/dynamic/[slug]/page.tsx (added, +16/-0)
• test/production/app-dir/build-output-tree-view/fixtures/dynamic-generate-static-params/app/layout.tsx (added, +11/-0)

---

PR #85135: feat(cache-components): require non-empty generateStaticParams for validation

• Repository: vercel/next.js
• Author: wyattjoh
• State: closed | merged: True
• Link: https://github.com/vercel/next.js/pull/85135

Description (problem / solution / changelog)

What?

This PR adds build-time validation that requires generateStaticParams to return at least one result when Cache Components (experimental cacheComponents feature) is enabled.

Why?

Previously, users could return an empty array ([]) from generateStaticParams to indicate a route should be treated statically without providing specific parameter values. This pattern has a critical issue with Cache Components:

The Problem:

• With Cache Components enabled, accessing params is treated as a dynamic API usage
• When generateStaticParams returns empty results, Next.js cannot perform build-time validation to detect if the route accesses other dynamic APIs (like await cookies(), await headers(), or await searchParams)
• This means users could successfully build routes that would fail at runtime with dynamic API errors

The Solution:

• By requiring at least one parameter value, we can execute the route during build time with real params
• This allows us to validate that the route doesn't make additional dynamic API calls that would cause runtime failures
• Build-time validation catches configuration errors early, before deployment

How?

• Modified buildAppStaticPaths in packages/next/src/build/static-paths/app.ts to check if PPR is enabled and throw error when generateStaticParams returns empty array with Cache Components enabled
• Added comprehensive error documentation at errors/empty-generate-static-params.mdx with migration options

Migration paths provided in error documentation:

1. Return at least one real param (recommended)
2. Use placeholder params (not recommended, bypasses validation)

The breaking change is acceptable because cacheComponents is still experimental and only available in canary releases.

Related

• Addresses discrepancy discovered with https://github.com/vercel/next.js/discussions/84925.
• Fixes https://github.com/vercel/next.js/issues/84801

Changed files

• errors/empty-generate-static-params.mdx (added, +69/-0)
• packages/next/errors.json (modified, +2/-1)
• packages/next/src/build/static-paths/app.test.ts (modified, +72/-28)
• packages/next/src/build/static-paths/app.ts (modified, +15/-3)
• packages/next/src/shared/lib/errors/empty-generate-static-params-error.ts (added, +13/-0)
• packages/next/src/shared/lib/errors/missing-default-parallel-route-error.ts (modified, +5/-7)
• packages/next/src/shared/lib/errors/usage-error.ts (added, +10/-0)
• test/e2e/app-dir/app-alias/src/app/typing/[slug]/page.tsx (modified, +1/-1)
• test/e2e/app-dir/app-catch-all-optional/app/[lang]/[flags]/[[...rest]]/page.tsx (modified, +1/-1)
• test/e2e/app-dir/not-found-with-pages-i18n/app/app-dir/[[...slug]]/page.tsx (modified, +1/-1)
• test/e2e/app-dir/sub-shell-generation-middleware/app/rewrite/[slug]/page.tsx (modified, +1/-1)
• test/e2e/app-dir/sub-shell-generation/app/[lang]/[slug]/page.tsx (modified, +1/-1)
• test/production/app-dir/empty-generate-static-params/empty-generate-static-params.test.ts (modified, +33/-17)
• test/production/standalone-mode/required-server-files/app/optional-catchall/[lang]/[flags]/[[...slug]]/page.jsx (modified, +1/-1)